Particle-Hemodynamics Simulations and Virtual Prototyping of Branching Blood Vessel

• In collaboration with Prof. Truskey at Duke University, we found detailed bio-physical mechanisms explaining the early stages of atherosclerosis using rabbits as a model; we developed hemodynamic wall parameters, which minimized, yield optimal bypass graft-to-artery geometries. As a result, we designed a new graft-end for hemodialysis patients, and provided in collaboration with Dr. Archie geometric recommendations for the surgical reconstruction of the carotid artery bifurcation. Furthermore, particle-hemodynamics analyses and virtual prototyping focused on femoral graft-to-artery anastomoses.

Toxic or Therapeutic Aerosol Transport and Uptake in the Respiratory System

• In collaboration with Dr. Kim at the U.S. EPA, and Dr. Donohue, Pulmonary Devision, UNC-CH, we pioneered realistic computer simulations of air flow and the deposition of toxic as well as therapeutic particles ranging in diameters from 1 nm to 15 micro-meter in multi-branch lung airways. The predictions of airway sites with excessive toxic particle depositions help scientists to correlate cause-and-effect scenarios for lung diseases. A large-scale application of our work on turbulent air flow and pollutant distribution was the redesign of human inhalation test chambers. Future work concentrates on the microscale simulation of toxic particles and drug aerosols in the entire respiratory system.
• Parallel to these investigations near-wall three-phase flow in the lung and species mass transfer into the lung tissue are being conducted. One result of this work is the design and prototyping of a smart inhaler system for drug-aerosol targeting in the nasal cavity and the lung.

Nanofluid Flow and Particle Transport in Micro-systems

• Nanofluids, a dilute suspension of nanoparticles in a liquid exhibit unusual thermodynamic properties, while "liquid flow in micro-conduits" pose a new challenge in accurate mixture flow simulation because of the very small length scales. In a recent series of articles, we analyzed contradictory experimental results on liquid flows in microchannels and proposed a new thermal conductivity model for nanofluids.
• While new micro-electro-mechanical systems (MEMS) are being constantly developed, fundamental research exploring their fluid-particle and heat transfer phenomena are still in their infancy. This open-ended research project is funded by the McDonald-Kleinstreuer Fellowship in Biofluid Mechanics.

Fluid-Structure Interactions as applied to Stented Aneurysms

• In collaboration with Dr. Farber, endovascular surgeon at UNC School of Medicine, abdominal aortic aneurysm (AAA) rupture criteria, causes of endovascular graft migration, and secure stent-graft placement are analyzed. Future work will focus on the design of new stent-grafts.

Optimal Designs of Medical Devices

• Our fundamental research results in conjunction with virtual prototyping techniques lead to improved medical devices or new applications. Examples include prosthetic blood vessels, inhalers of drug aerosols, stents, nano-therapeutic devices, and non-intrusive bio-MEMS.

Terascale Analysis and Teragrid Computing of Complex Biofluid Dynamics Systems

• Some of our biofluid dynamics projects require unusual HPC resources, i.e., tera-scale computing is necessary. The specific tera-scale research objectives are as follows:

• This multidisciplinary, multi-task project is driven by a quest for a deeper understanding of human health issues involving pulmonary and vascular systems that are governed by complex biofluid dynamics. Problems of this magnitude and complexity can only be attempted by a concerted effort and innovation in three fundamental/applied research areas: biofluid dynamics systems and health issues, models and theory, and network enabled high-end computing. The research and software development activities will target three important biofluid dynamics applications: particle transport and deposition in the human conducting zone, including drug aerosol delivery, blood flow and optimal femoral bypass graft design, as well as microfluidics and bio-MEMS. Current studies are limited to simplified geometries analyzing small aspects of the actual systems.
  

• In the area of high-end computing, a modularized framework will be utilized to develop interoperable mesh generation, fluid flow, heat transfer, and particle transport. For each module, scalable parallelization strategies (both in terms of memory and performance) will be employed to take advantage of a wide range of parallel architectures ranging from SMP cluster architectures to workstation clusters. Use of grid computing resources, such as the Teragrid employing geographically distributed resources, will be rigorously investigated for solving large-scale fluid-particle dynamics systems as well as nano-scale systems, employing a molecular dynamics approach (DSMC or LBM).
  

• Findings, including flow visualization movies, from the project can be incorporated into graduate courses in biomedical and mechanical engineering, high performance computing, and computational fluid dynamics. In addition to the clinical importance of the proposed research, it is also expected to contribute to many basic science areas: simulation of complex biofluid dynamic systems (biomedical side), development of realistic mathematical/numerical models (computational fluid dynamics side), and parallel algorithms for efficiently utilizing modern terascale computing environments (IT side).